Promethazine is an antihistamine that can be used off‑label for cough suppression, but it is not FDA‑approved for this purpose in the United States. Because it can cause drowsiness, anticholinergic effects, and in some cases respiratory depression (especially in young children), the dose and use should be determined by a qualified healthcare provider.
---
Typical Adult Dosing (for cough‑suppression, if prescribed)
| Form | Common Dose | Frequency | Max Daily Dose |
|------|-------------|-----------|----------------|
| Oral tablets or syrup | 25 mg | every 4–6 hours as needed | ≤ 150 mg/day |
| Intramuscular (IM) | 25–50 mg | once or as directed | 150 mg/day |
The above is a typical “start low, go slow” regimen. A clinician may adjust the dose based on patient weight, liver function, comorbidities, or concomitant medications.
---
Typical Pediatric Dosing (if a clinician deems it appropriate)
| Age | Dose (per kg) | Max dose | Frequency |
|-----|---------------|----------|-----------|
| 2–12 yr | 0.5–1.5 mg/kg | ≤ 8 mg/kg | every 4–6 hours |
Important
- Do NOT use promethazine for cough in children under 2 years or in patients with a history of seizures or breathing difficulties.
- The max daily pediatric dose (for 2–12 yr) is ≤ 8 mg/kg; do not exceed this, and never exceed 150 mg/day in any age group.
---
Key Safety Notes
| Issue | Recommendation |
|-------|----------------|
| Sedation | Avoid driving, operating heavy machinery, or alcohol while on promethazine. |
| Respiratory Depression | Highest risk in infants, young children, and patients with asthma or COPD. |
| Anticholinergic Effects | Dry mouth, blurred vision, constipation, urinary retention—more pronounced in the elderly. |
| Drug Interactions | May potentiate CNS depressants (opioids, benzodiazepines, barbiturates). Avoid concomitant use of CNS depressants without supervision. |
| Contraindications | Recent surgery involving the eye or nasal passages, acute angle‑closure glaucoma, severe liver disease, or hypersensitivity to the drug. |
| Pregnancy/Lactation | Use only if clearly needed; promethazine passes into breast milk. |
---
Bottom Line
- Promethazine can be prescribed for cough in some adult or pediatric patients, but it is not a first‑line or FDA‑approved cough remedy.
- Dosing should be individualized by a prescriber: 25 mg PO every 4–6 hours for adults (≤ 150 mg/day) and 0.5–1.5 mg/kg (≤ 8 mg/kg/day) for children 2–12 years.
- Always consult a healthcare professional before starting, changing, or stopping any medication, especially in children, pregnant or nursing women, or patients with chronic illnesses.
If you’re experiencing persistent cough or have questions about the best therapy for your situation, talk to your doctor or pharmacist. They can consider all safety factors and alternative cough‑relief options.